Autism Spectrum Disorders (ASDs) are increasingly being diagnosed. ASDs are a collection of linked developmental disorders, characterized by abnormalities in social interaction and communication, restricted interests, and repetitive behaviours. In addition to classical autism or Autistic Disorder, the fifth edition of the American Psychiatric Association's (APA) Diagnostic and Statistical Manual of Mental Disorders (DSM-5) recognizes Asperger syndrome, Childhood Disintegrative Disorder, and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS) as ASDs.
Neurodevelopmental Disorders (NDDs) include Fragile X Syndrome (FXS), Angelman Syndrome, Tuberous Sclerosis Complex, Phelan McDermid Syndrome, Rett Syndrome, CDKL5 mutations (which also are associated with Rett Syndrome and X-Linked Infantile Spasm Disorder) and others. Many but not all NDDs are caused by genetic mutations and, as such, are sometimes referred to as monogenic disorders. Some patients with NDDs exhibit behaviors and symptoms of autism.
As an example of a NDD, Fragile X Syndrome is an X-linked genetic disorder in which affected individuals are intellectually handicapped to varying degrees and display a variety of associated psychiatric symptoms. Clinically, Fragile X Syndrome is characterized by intellectual handicap, hyperactivity and attentional problems, autism spectrum symptoms, emotional lability and epilepsy (Hagerman, 1997a). The epilepsy seen in Fragile X Syndrome is most commonly present in childhood, but then gradually remits towards adulthood. Hyperactivity is present in approximately 80 percent of affected males (Hagerman, 1997b). Physical features such as prominent ears and jaw and hyper-extensibility of joints are frequently present but are not diagnostic. Intellectual handicap is the most common feature defining the phenotype. Generally, males are more severely affected than females. Early impressions that females are unaffected have been replaced by an understanding of the presence of specific learning difficulties and other neuropsychiatric features in females. The learning disability present in males becomes more defined with age, although this longitudinal effect is more likely a reflection of a flattening of developmental trajectories rather than an explicit neurodegenerative process.
The compromise of brain function seen in Fragile X Syndrome is paralleled by changes in brain structure in humans. MRI scanning studies reveal that Fragile X Syndrome is associated with larger brain volumes than would be expected in matched controls and that this change correlates with trinucleotide expansion in the FMRP promoter region (Jakala et al., 1997). At the microscopic level, humans with Fragile X Syndrome show abnormalities of neuronal dendritic structure, in particular, an abnormally high number of immature dendritic spines (Irwin et al., 2000).
Currently available treatments for NDDs are symptomatic—focusing on the management of symptoms—and supportive, requiring a multidisciplinary approach. Educational and social skills training and therapies are implemented early to address core issues of learning delay and social impairments. Special academic, social, vocational, and support services are often required. Medication, psychotherapy or behavioral therapy may be used for management of co-occurring anxiety, Attention Deficit Hyperactivity Disorder (“ADHD”), depression, maladaptive behaviors such as aggression, and sleep issues. Antiepileptic drugs may be used to control seizures.